Underground conduit for electrical conductors



Patented Nov. 29, |898.

C. H. SEWALL. UNDERGROUND CONDUIT FOR ELECTRICAL GONDUCTDRS.

(Application led Mar. 2, 189B.)

(No Model.)

me uonms mins coyuorouwmwnsn UNITED STATES ATENT rricn.

CHARLES II. SEVVALL, OF CHICAGO, ILLINOIS.

UNDERGROUND CONDUIT i-V'OR ELECTRICAL CONDUCTORS;

SPECIFICATION forming part of Letters Patent No. 614,995, dated November29, 189e.

Application iiled March 2, 1898. Serial No. 672,246. (No model.)

To all whom z5 may concern.-

Be it known that I, CHARLES H. SEWALL, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Underground Conduitsfor Electrical Conductors, of which the following is a full, clear,concise, and exact description, reference being had to the accompanyingdrawings, forming a part of this specification.

My invention relates to underground conduits for electrical conductors,my object being to provide an effective form of conduit that may beeconomically constructed, while possessing all of the desirablequalities as to mechanical construction and electrical installation.

My invention has more particular reference to those classes ofunderground conduits wherein the conduit-ducts are formed or embedded ina body or mass of hydraulic concrete or similar material. When hydraulicconcrete or mortar is employed, it is desirable to maintain the concretemoist, as thereby a stronger and firmer mechanical structure results.The moisture in the concrete may be secured from the atmosphere as theair is drawn through the conduit from one manhole to another, as isusually the practice, the water of condensation from the air thusserving to maintain the mass of concrete uniformly moist. The presenceof the moisture in the concrete also results in desirable electricalproperties, such as the prevention of condenser action. The moistureserves, for instance, to bond together the lead sheaths of the cables inthe conduits, thus reducing the insulation resistance between thesheaths of the cables and materially reducing the tendency of inducingcurrents from one cable to another. This is especially advantageous intelephone construction, where the presence of even small inducedcurrents results in defective operation of the telephone system. Theremaybe instances, however, wherein the presence of moisture in theconcrete will be found objectionable--as, for instance,when the conduitis in proximity to an electric railway, Where leakage takes place fromthe rails through the earth. In such cases it may happen that theextraneous currents thus passing through the earth will penetrate themass of concrete due to the moisture therein and traverse the sheaths ofthe cables in the conduits, thus resulting in electrolytic corrosion atpoints where the extraneous currents pass from the metallic sheaths toan electrolyte-a in the present instance lthe moisture in the concrete.To obviate any such difficulty, I surround the mass of hydraulicconcrete or similar material by a layer or sheath of insulatingmaterial, such as asphalt or bituminous concrete, to eifectivelyinsulate the hydraulic concrete and the moisture therein from the earth.Should induced currents be found present in the sheaths of the cables,they may be readily carried off by bonding the sheaths of the cablestogether at the manholes and connecting the same to ground at a pointbeyond the ield of any extraneous currents.

In accordance With the present invention I surround the foundation andinclosure of hydraulic concrete or other conduit-carrying material bymeans of a layer of insulating material, such as asphalt or bituminousconcrete, whereby the hydraulic concrete is insulated from thesurrounding earth, and, while retaining the desirable water ofcondensation, is removed from contact with the earth, whereby the Waterof condensation is prevented from forming a path for extraneous currentsthrough the body of concrete. I may form the insulating sheath or layerin any desired manner, as by pouring asphalt or bituminous concrete orthe like material around the hydraulic concrete and permitting the sameto cool to form a continuous and jointless sheath, or by previouslyforming slabs or planks of bituminous concrete or the like material,which are laid in the trench with the joints sealed by plastic material,after which the conduit is built up, the upper wall of the hydraulicconcrete being in a similar manner covered by the slabs or planks andall the joints being effectively sealed. In this manner the hydraulicconcrete is thoroughly insulated from the earth. The moisture drawn inthrough the conduits from the external air will be found sufficient tocompensate for any evaporation of the water of condensation of thehydraulic concrete, and will thus maintain the hydraulic concrete in thedesirable moist condition, which thus in IOO n`o manner impairs theelectrical properties of the conduits.

I preferably construct the conduits in accordance with the plan shown inan application filed by me May S, 1805, Serial No.

lSlS, wherein inverted channels are employed which may be made of anydesired material and which for mechanical reasons are usually made inshort lengths or sections adapted to be placed end to end to form aprolonged cond uit, thus giving rise to the necessity of providing` someconvenient and effective bridge adapted to be placed over the joints,thereby effectively connecting the adjoining sections together when theinclosing body of concrete is placed in position. In said application Ihave described an archshaped bridge which may be made of woven wire orother open frame of metal or other material, as reeds, or clothshellacked to impart rigidity thereto, the frame being adapted to beplaced over the joint upon the exterior of the sections, so that thebridge is molded into the surrounding body of concrete, and thus holdsthe sections securely in position. I have experienced difficulty inpreventing the plastic concrete from passing through the cracks betweenthe adjoining ends of the sections, and in order to prevent this I haveprovided upon the bridge, upon either the exterior or the interior face,a medial band orstrip of cloth, paper, or other material adapted tocover the joint or crack, and thus prevent the plastic concrete frompassing therethrough.

My invention further contemplates an improved form of inverted channeladapted to be placed upon the continuous floor of indeiinite width andlength, the inverted channel comprising a block having a plurality ofchannels or grooves on the under face to form conduit-ducts when placedupon the floor, the blocks being molded into the inclosing body ofconcrete.

I have illustrated my invention in the accompanying drawings, in Which-Figure lis a transverse sectional View illustrating the conduit of myinvention. Fig. 2 is a view illustrating two sections of the invertedchannels placed in position with the bridge covering the joint. Fig. 3is a View of the bridge. Fig. l is a sectional view of the preferredform of the inverted channel. Fig. 5 is a view of an inverted channel orblock having a plurality of conduit grooves or channels.

Like letters refer to like parts in the several figures.

I have illustrated my invention in connection with the structure which Ihave adopted in practice, wherein the inverted channels are molded insections a a with an intermediate layer of woven wire l) or otheropenmetallic frame to afford strength to the structure, the plastic materialof which the section is formed being preferably of hydraulic concrete.The present invention, however,

as to the insulating-sheath is equally applicable to conduits of otherforms. In the formation of the conduit a trench is dug, upon the bottomof which are placed a series of planks or slabs c c, of bituminousconcrete, the sides of the trench being likewise lined With similarslabs or planks c c. Upon the bottom slabs is placed a body orfoundation CZ, of hydraulic concrete, a floor being formed upon thesurface thereof, preferably by sprinkling fine sand and cement thereoverand smoothing and polishing the same to make a smooth floor which Willfacilitate the drawing of the cables through the conduits. Upon thecontinuous door thus formed, which may be of an indefinite Width andlength and which preferably extends across the trench, are placed anumber of inverted channels a a, and a second body of hydraulic concreted/ is placed upon the inverted channels to inclose and surround thesame, the concrete during the drying and setting thereof forming itselfintegral with the foundation of concrete along those portions of thefloor exterior to the conduits, whereby the conduits are surrounded andinclosed by an integral and continuous body of concrete. IVhere a secondtier of conduits is to be formed a iioor is formed upon the surface ofthis second body of concrete d', upon which are placed a second seriesof sections a a, which in turn are inclosed within a third body ofconcrete d2, which forms the foundation of a third tier of invertedchannels inclosed by a body of concrete d3, and so on for the desirednumber of tiers. Upon the top of the body of concrete as thus formedslabs c c of bituminous concrete are placed and the trench is theniilledA The joints between the slabs c c are sealed by means of plasticasphalt or bituminous concrete, thus inclosing the body of hydraulicconcrete in a continuous and unbroken sheath of insulating materiahwhichprevents the passage of Water or moisture and which also prevents thepassage of earth-currents.

As the inverted channels ct a are placed in position end to end, Fig. 2,a bridge cis placed in position over each of the joints, the bridgecarrying a strip e of cloth, paper, or the like to cover the joint andprevent the passage of concrete therethrough. This strip may be placedupon either face of the bridge; but I preferably place the strip e uponthe exterior of the bridgefvvhile upon the interior is placed a narrowstrip e2, which is pasted or glued to the exterior strip at intervals,whereby the exterior strip is held securely in position. The bridge, asbefore stated, may be made of metal or may be formed of reeds or fromcloth, in any case a medial band or strip being provided adapted to iitover and seal the joint against the entrance of the plastic inclosingmaterial.

In Fig. 5 I have illustrated a form of inverted channel or block inWhich a plurality of conduit channels or grooves are provided. Theblocks are made in sections and placed end to end to form a plurality ofprolonged IOO IIO

conduits. The blocks or channels are placed upon the continuous door ofindefinite Width and length formed on the surface of the foundation, asabove described, and are then surrounded and inclosed by a body ofconcrete, which may form the foundation for a second inverted channelwhen desired. The inverted channels may thus be provided with aplurality of conduit-grooves, as shown in Fig. 5, or may be providedWith a single groove, as shown in Fig. l. In each case the invertedchannel is placed upon the iioor and then covered With the plasticmaterial, which forms integral with the foundation to form an inclosingbody of integrally-formed material. Bridges may be placed over thejoints, as before described, the bridges being shaped to fit theparticular contour of the blocks. In this figure the inclosing sheathcis shown as continuous and jointless.

Having described my invention, What I claim as new, and desire to secureby Letters Patent, is

l. The combination with a body of material having a conduit or conduitsinclosed therein, of an inclosing layer or sheath of insulating materialcompletely surrounding said body of material on the top, bottom andsides and effectively insulating the same from the earth to prevent theaccess of extraneous currents to the inclosed body of material,substantially as described.

2. The combination With a body of hydraulic concrete, or similarmaterial, having a conduit or conduits inclosed therein, of an inclosinglayer or sheath of bituminous concrete, or similar insulating andimpervious material, completely surrounding said body of hydraulicconcrete on the top, bottom and sides to prevent the passage ofextraneous currents to the sheathing of the cables in the conduits,substantially as described.

3. The combination with a foundation of hydraulic concrete, or similarmaterial, having a floor formed on the surface thereof, of a series ofinverted channels thereon placed end to end, a body of hydraulicconcrete, or similar material, inclosing and surrounding said invertedchannels and formed integral with said foundation, and a layer or sheathof bituminous concrete or similar material inclosing and surroundingsaid mass of hydraulic concrete and insulating the same from the earth,substantially as described.

4. The combination with a foundation having formed upon the surfacethereof a continuous floor of indefinite Width and length, of aninverted channel or block resting thereon and having a plurality ofconduit-grooves therein, substantially as described.

5. The combination with a foundation of plastic material adapted toharden and set and having formed upon the surface thereof a continuousfloor of indefinite width and length, of an inverted channel or blockresting thereon and having a plurality of conduit-grooves therein, and abody of plastic material inclosing and surrounding said in- Vertedchannel or block and formed integral with said foundation, substantiallyas described.

6. The combination with a series of conduit-sections adapted to beplaced together end to end, of a bridge formed of an open frame adaptedto be placed over the joint, and a medial strip or band to prevent thepassage through the joint of the material surrounding the sections,substantially as described.

7. The combination with a series of conduit-sections adapted to beplaced together end to end, of a bridge formed of an open frame adaptedto be placed over the joint, and a pair of strips or bands of cloth orthe like, one upon the exterior and the other upon the interior face ofthe bridge said strips being secured together through the apertures insaid bridge, substantially as described.

In witness whereof I have hereunto subscribed my name in the presence oftWo Witnesses.

CHARLES H. SEWALL.

